Spring loaded seal



July 12, 1960 G E COLBY v 2,944,843

SPRING LOADED SEAL Filed Aug. 8, 1957 q: 7 l i 57 da 45' 53 33 57 34 554; 5,6 Eig. l' I Ge og@ E( BY mwgaguw ATTORNEY .5.

`certain environments. ,with rotating members such as shafts which are-in turn f 2,944,843, n y 1 y SPRING LoAnnpsEAL VGeorge E. Colby,`Barrington',`R.I.,` assigner to Magnetic Seal Corp., 'a corporation ofRhode Filed VAug. 8, V1957, Ser.; No).l 677,075 Y Y 4 claims. (c1.2st-11.14)

,c States ,atent cross connected to some form of machinery. Every form Habout its position of equilibrium. The frequency of this oscillationexpressed as Fn is called the natural frequency of the mass on thespring and is given by the equation where Fn is the natural yfrequencyexpressed in cycles per second, K is the spring constant or force perunit deflection of the spring expressed in poundals per foot deection,and M is the mass in pounds.

Theoretically, if the vibrations from the machine are impressed upon themass of a spring loaded seal and allowed to work in a 4free system,which is the ideal case, the mass will vibrate forever. Of course, thisnever occurs in nature for all `free vibrations die down in time, due tosome form of damping. With any form of damping, however, it will beapparent that the spring will undergo quite a -few excursions unlesswhat is known as critical damping is reached. Critical damping mayusually be described as the phenomena in which when a force is appliedto the mass, the spring will not undergo an excursion that carries itbeyond the equilibrium point. Critical damping has been expressedmathematically as It is further known that any material that undergoesvibratory excursions will fatigue after a certain number of theseexcursions, that is, after a certain number of excursions have takenplace in any material, such as metal, the crystalline structure of themetal will change considerably to develop lines of less adhesion fromone crystal interface to the other. lt is desirable, therefore, tocompletely reduce this fatigue in a seal of the general form describedabove, and thus we are concerned with critically damping a spring loadedseal by exerting upon the spring in some manner a force which will giveus critical damping'. In accordance with the present invenl l It is,therefore, an object of this invention to construct a spring loaded sealhaving critical damping.

AV further object of the invention is to construct a seal in which thereare two relatively rotating parts that are Aspring'loaded and in whichan additional force is exerted uponthe seal between the stator'androtorthat will give us a critical damping factor forthe spring.

With'these and other objects in'view, the invention consistsof certainnovel features of construction, as will be more fully described andparticularly pointed out in the appended claims. -In the drawings: j

Fig. 1 is a sectional view taken through a seal of the general typedescribed; .1..

Fig. 2 is a sectional viewof the spring utilized in this construction;

Fig. 3 is a sectional view showing a modified form of a seal of thegeneral construction referred to; and

Fig. 4 is an edgeview of a modied form of spring.

Referring now to the drawings, 10 designates generally a housing inwhich a iluid is to be sealed against escape about a rotary shaft 11which passes therethrough. This housing is preferably constructed of amaterial which does not exhibit magnetic properties, such asnon-magnetic stainless steel, and is provided with a bore 13therethrough which has -a reduced section 14 thereof providing ashoulder 15 extending in a plane at right angles to the axis of thebore. Within the bore 13, there is .provided a ring 16 having a lip 16which abuts the shoulder 15, the entire ring being held stationary withrespect to the housing I10. Within this ring 16, there is received arotary seal designated generally 17.

The rotary seal comprises a collar 18 which is attached to the shaft y11Vand is provided with a sealing` surface 19. The sealing surface 19extends in a plane at right angles or normal to the axis of the shaft 11and is machined to within 2.3.2)(10-6 inch or 2 helium bands ilat asviewed with an optical flat under a monochromatic light source.Co-operating with the collar 1S is a ring part 20 which surrounds theshaft 11 in spaced relation thereto and is preferably madefrom apermanent magnetic alloy such as Alnico V, which alloy consists ofaluminum, cobalt, copper and iron materials. The part 20 has an annulargroove 21 in which is received an 0ring gasket 22 that abuts the ring 16to effect a fluid tight seal between the ring 16 and the part 20. Thepart 20 has afixed thereto in its inner diameter a carbon ring 23 whichhas an ann-ular lip 24 provided with a sealing surface 25 that abuts thesealing surface 19 by the force of the spring 26. The spring 26prefer-ably takes a ring formation having an undulated surface, theundulations abutting against the lip 16' of the ring 16 and the part 20.The ring part 20 and its carbon ring 25 are effectively stationary withrespect to the housing 10 and the ring 16. Fluid entering the housing 10from the right hand side, as viewed in the drawing, is blocked fromescape therefrom by the 0ring seal 22 and the seal between the faces 19and 25.

inasmuch as the part 20 is made from magnetic material as noted above,the force of this magnet may be dened with respect to the collar 18 sothat it is ineffective to provide a tight seal between the surfaces 19and 25. Spring 26, therefore, provides the actual force to eect the sealbut in practice, this force has been found to give uneven pressure; andfurther, the spring under certain vibration conditions will tend toresonate and exhibit a deflection which is variable. The magnetic ring2i) in this case tends to dampen these vibrations Vand exerts asufficient pull toward rotor 18 to provideV the critical damping of thespring 26.

Referring to Fig. 3, I have shown a modified form of a seal which isparticularly adapted to be utilized where a balanced seal is desired.This seal arrangement consists of a housing 30 having a bore 31. Arotary seal desigi Y part 33. The part 33 comprises a -magnetierin'gwhich l,

i's'fmade of amagnetic alloy such as Alnicoh` Af'st'e'e'l collar 34 is'provided with Aa groove 37` whichreceives an O-ring 38 to `form a fluidtight seal between the shaft 11 andthe collar 34;k An annularlip'39'extends from 'the collar 34 and forms on' one side thereof arecess-@that vreceives a carbon ring insert 41 which is lprovided with a'Y sealing surface 42. In this particular embodiment, fthe shaft 11 isreduced and thereby forms a shoulder 1l. Between the lip 39""andthisshoulder 11', there is received an annular spring 43 which 'has -a'nundulated surv face so that tabuts the shoulder lljand the lip 39. f

This spring thereby forces the part 34 toward the part 33 and provides asealing surface between the surface 42 of the carbon 'ring and thesurface 33 of the part 33. VThese sealing surfaces referred to are in aplane at right angles or normal to the axis of the shaft 11 and aremachined ilat to within 23.2 l0F6 inch. The seal operates in the samemanner as the embodiment described above, except in this case the collar34 is provided with surfaces that are normal tothe shaft 11 that ineffect provide equal areas in the axial direction of the sha-ft asviewed Vfrom the left or the right, thus Aeffectively placingthe part'34 in a fluid equilibrium. The equilibrium is secured by sizing areasas follows: the surface area on member 34 exposed to the pressure of theuid acting thereon in a direction tending to Ymove the sealing surfacesinto engagement is a surface area equal to a surface area of diameter Dminus diameter d', the surface area onY member 34 exposedto the saidfluid pressure acting thereon in a direction tending to move the saidsealing surfaces apart is av surface area equal to a Vsurface areaof'diameter D l'minus diameter d. Thus, since Adiameter d is made equalto diameter d', the sealing member 34 is inba-lance to the fluidpressure sealed. Y

The spring 26 or 43 in cases where there is plenty of 4 axial room maybe a wire coil about the shaft several `turns in place 'of lthe wavy-spring of Fig. 2 as seen lin Fig. 4 at 45. v L.

I claim:

1. A fluid seal device for effecting a fluid-tight seal between tworelatively rotatable members, sealing faces on said members, resilientmeans urging said faces into sealing engagement, and magnetic meansurging said members into sealing engagement, said magnetic meansexerting `a force suicient to critically dampen said resilientmeans andlessfthan the force required to forma ilu-id tight seal` between saidfaces.

2. A duid' seal device for effecting a duid-tight seal between arotatable shaft and a housing therefor, said seal comprising a collar on-the shaft andl rotatable therewith, said collar having a sealingsurface disposed in a plane perpendicular to the axis of the shaft, anannular part surrounding said sha-ft mounted in said housing in sealingengagement-therewith, said annular part having a sealing' surface'disposed in a plane perpendicular to the axisv of the shaft, resilientmeans holding said annularpart against 'said collar,'sai'd annular partbeing wholly of a magnetized material tobe attracted-toward said collar,themagnetization force *being sufficient te Acritically damp saidresilient `means and less titan-that required to -form a duid tight sealbetween said surfaces.

3. A fluid vseal device as in claim l wherein said Yresilient means isan annular undulated spring.

4. A fluid seal device as in claim l wherein said resilient means Iis anannular lcoiled spring.

"References Cited in -the file fof this Apatent UNITED STATES PATENTS1,339,156 Beldarn May 4, 1920 2,365,046 Bottomley Dec. 12, 19442,672,357 VOyteCh Mar. 16, 1954 2,685,463 Pollard Aug. 3, 1954 2,706,652Berger Apr. 19, 1955 2,738,208` Mylander Mar. 13, 1956 f Y FOREIGNPATENTS Great Britain Sept. 10, 1952

